1. Technical Field
The present invention relates to an additive composition for asphalt emulsion, a composition for asphalt emulsion and a composition for emulsification which are used for the preparation of an asphalt emulsion; an oil-in-water asphalt emulsion; a paving composition comprising aggregate and an oil-in-water asphalt emulsion; and a process for the preparation of the above composition for emulsification. The asphalt emulsion according to the present invention is excellent in stability as emulsion and mixability with aggregate, and is easy to control the decomposition time thereof, and the products (mainly asphalt) of breaking of the emulsion are excellent in adherence to aggregate. Further, the constructions executed by the use of the emulsion are excellent in stripping resistance. Other asphalt emulsions according to the present invention are used by mixing it with aggregate in plant or place in the use of open grade mixtures, dense grade mixtures, slurry seals, sand mixtures, reclaimed mixtures and so on, are excellent in stability as emulsion, mixability with aggregate and mixability with cement, and is easy to control the decomposition time thereof, and the products (mainly asphalt) of breaking of the emulsions are excellent in adherence to crushed stone. Further, the constructions, such as pavement, executed by the use of the emulsions are excellent in strength, endurance and stripping resistance.
2. Description of the Related Art
Bituminous materials obtained from petroleum, e.g., asphalt, tar and pitch, have widely been used from old as a paving material, a waterproof material and an adhesive and in the construction of railroads. However, bituminous materials are very poor in workability when used as such, owing to their extremely high adhesivenesses. Therefore, bituminous materials are used after their flowabilities are enhanced by a means such as heating (i.e., heat melting process), treatment to be in the form of emulsion by using a proper emulsifying agent and water, and dissolution in a suitable solvent, for securing a desirable workability
Among such emulsions of bituminous materials, aqueous emulsions of asphalt are generally called "asphalt emulsions". Such the asphalt emulsions are roughly classified into fast-decomposing emulsions (i.e., emulsions for application) which are directly applied to the object surface, and slow-decomposing ones (i.e., emulsions for blending) which are blended with aggregate. Although the surfactant to be used in the preparation of an asphalt emulsion is suitably selected from among anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants, the kind thereof is generally determined depending upon the process of execution thereof.
Among the above asphalt emulsions, one for blending is mixed with aggregate, a filler and other components. The asphalt composition thus prepared is used for the construction of paving of a road. The so-called emulsion breaking is caused by the evaporation and elimination of aqueous components in the composition, after the execution of a road by using an asphalt composition. Thus, the asphalt is hardened to complete the construction of paving of a road.
Further, the kind of paving of a road to be formed and the properties and performance thereof vary depending upon the kind of aggregate to be used together with such the emulsion for blending. For example, an asphalt composition (an open grade mixture) comprising an emulsion for blending and an open grade aggregate is used in the execution of upper and lower subbases, or in the execution of surface drainage course. While an asphalt composition (a dense grade mixture) comprising an emulsion for blending and a dense grade aggregates is used in the execution of upper subbase or surface course. Further, a composition prepared by mixing an emulsion for blending with a fine aggregate or filler is used as slurry seal for the purpose of restoring a deteriorated area of pavement, and a composition (a sand mixture) prepared by mixing it with sand is used for forming a simple surface course. It is also conducted to mix an emulsion for blending with crushed paving (a reclaimed mixture), for the re-use of deteriorated and existing paving. Meanwhile, the mixing processes for preparing such the asphalt compositions include two processes, i.e., in-plant mixing and in-place mixing, and they are used properly and suitably depending upon the conditions.
In the execution of a road by using an asphalt emulsion for blending, the asphalt which is re-generated by breaking the asphalt emulsion adheres to aggregate to act as a binder among the aggregate, by which the strength and endurance of paving of a road are exhibited. Meanwhile, as described above, an asphalt emulsion for blending contains a surfactant. An emulsion containing, among surfactants, an anionic surfactant or a nonionic surfactant has a significant disadvantage in that the products, mainly asphalt, of breaking of the emulsion are poor in adherence to aggregate, though the emulsion has such an advantage that it exhibits good mixability with aggregate. On the other hand, a cationic surfactant accelerates the adhesion of asphalt particles to aggregate by the electric attractive force thereof. However, paving of a road executed by the use of an asphalt emulsion containing a cationic surfactant is also poor in strength and endurance. Thus, it has become a common opinion that every paving of a road executed by the use of an asphalt emulsion is poor in strength and endurance. Although the strength and endurance of paving of a road executed by the use of an asphalt emulsion are, as described above, exhibited by the adhesion of asphalt to aggregate, the strength and endurance of paving of a road exhibited by the use of a current asphalt emulsion are insufficient, and measures for improvement by which higher strength and endurance can be realized are desired.
Additionally, it is required for an asphalt emulsion for blending to have such performances that the stability of the emulsion is excellent when a forced mechanical agitation is conducted, that it does not cause separation (i.e., an emulsion breaking is not occurred) during execution such as transportation, spreading and rolling, that it is separated (i.e., the emulsion is broken) at a somewhat high speed after paving, that the products of breaking of the emulsion is excellent in adherence to aggregate, and that these various properties are not affected by the kind of aggregate, atmospheric temperature at execution and so on. As measures for satisfying these requirements, there have been proposed the use of a large amount of an emulsifier (surfactant), the use of many kinds of emulsifiers, and the addition of a water-soluble organic polymer, e.g., polyvinyl alcohol, gelatin, methylcellulose, polyacrylamide or guar gum, to an asphalt emulsion as a protective colloid. An asphalt emulsion is stabilized by carrying out such measures. However, by carrying out these measures, such the effect that the adherence of the products, mainly comprising asphalt, of breaking of the emulsion to aggregate is essentially improved by the improvement of the properties of interface between aggregate and asphalt, is attained.
Various methods for improving the various properties of an asphalt emulsion have been proposed in addition to the those described above.
For example, there have been proposed the use of an aminated lignin, an alkylimidazoline compound and a nonionic emulsifier (see U.S. Pat. No. 3,871,893), that of a fatty acid salt of an alkylimidazoline compound (see U.S. Pat. No. 3,979,323), and that of a specific nonionic emulsifier (see Japanese Patent Publication-A No. Hei 7-118538) for improving the mixability of an asphalt emulsion with aggregate and the adherence properties of the products of breaking of the emulsion to aggregate. By these techniques, the mixability of an asphalt emulsion with aggregate is improved. Even when such an asphalt emulsion is used, however, the adherence of asphalt to aggregate and the stripping resistance of paving executed are insufficient owing to the intervention of water. Thus, the paving does not exhibit sufficient strength and endurance, only by measures of selecting the surfactant. Further, Japanese Patent Publication-A No. Sho 57-42763 and U.S. Pat. No. 3,867,162 disclose the use of a saturated fatty acid and that of tall oil fatty acid, respectively. However, an asphalt emulsion containing such an organic acid cannot be used in the case wherein cement or ferrous slag, which is basic, is used. Additionally, it cannot be expected under the current circumstances wherein lowering in the quality of road asphalt or aggregate is apprehended and, on the other hand, the use of reclaimed materials also spreads that excellent mixability of the emulsion with aggregate and firm adhesion of the components, such as asphalt, in the products of breaking of the emulsion to aggregate are exhibited by the use of an asphalt emulsion containing such an organic acid.
It is described in Japanese Patent Publication-A No. Sho 63-17960 that by allowing an asphalt emulsion to contain tannic acid or a tannin compound, the mixability of the emulsion with aggregate, the adherence of, e.g., asphalt to aggregate, and the stripping resistance of the paving which has been executed with the use of the emulsion are improved, and the decomposition time of the emulsion is prolonged. In an asphalt emulsion containing tallow-alkyl propylene-diamine, polyoxyethylene tallow-alkyl propylenediamine or stearyltrimethylammonium chloride which is a cationic surfactant, which is described in the above Publication, the delay of the decomposition time thereof is certainly attained by the addition of tannic acid. However, even in such the case, the decomposition time is still too short for the use of the asphalt emulsion as one for blending. Further, when tannic acid or a tannin compound is to be contained in an asphalt emulsion containing a nonionic surfactant such as polyoxyethylene nonylphneyl ether or an anionic surfactant such as sodium oleate, the adherence of the components such as asphalt in the products of breaking of the emulsion to aggregate is remarkably lowered, and thus the sufficient strength and endurance of a paving can not be obtained, though the mixability of the emulsion with aggregate is improved.
As described above, there has not been known an asphalt emulsion which is one to be used for the preparation of a composition (for example, an open-grade mixture, a dense grade mixture, a slurry seal, a sand mixture or a reclaimed mixture) for paving a road comprising an asphalt emulsion for blending and aggregate and which satisfies all of the properties including stability as emulsion, mixability with aggregate, easiness of controlling the decomposition time, adherence of the products of breaking thereof to crushed stone, and stripping resistance, strength and endurance of the paving executed by the use of the emulsion, the development thereof has been eagerly desired and the development thereof has been highly expected.